Conventional optical accelerometers are manufactured from discrete components that are used to direct light in various directions in order to ultimately measure acceleration based on changes in the light. Each of these discrete components is manufactured separately and is placed at a different location on the accelerometer body. Typically, some of these components include polarizers, polarized beam splitters (“PBS”) and static mirrors that direct the light beam towards different detectors and moving parts (e.g., a proof mass mirror or flexured mirror).
The conventional optical accelerometers measure acceleration using a Michelson interferometer assembly. Each of the discrete components must be carefully aligned to direct a light towards a measurement assembly. The components must also be positioned and aligned to receive the light and split it to produce various light beams of different phases. Some of the split beams are directed towards a detector and the other beams are directed towards a flexured mirror. The beams are reflected by the flexured mirror and then passed through PBS which must be aligned to combine the reflected beams with the beams not reflected by the flexured mirror. The PBS must also be aligned to direct the combined beams towards a detector that ultimately determines acceleration based on phase changes of the received beams.
The discrete components required in the measurement assembly typically occupy a large amount of space making it difficult to provide precise measurements of acceleration. Moreover, the discrete components are difficult to position and align to provide the desired behavior and are subject to be misaligned with changes in external conditions. More accurate measurements can be provided with multiple measurement assemblies. However, size limitations of the accelerometers restrict the ability to manufacture multiple measurement assemblies.
Additionally, phase differences in conventional systems are detected using commercial electronics such as operational amplifiers which can output imprecise values resulting from minor changes in environmental conditions, for example, temperature. Moreover, the PBS creates leakage light which can mix with principal waves and add coherently to create a nonlinear spurious acceleration signal. Removing errors caused by this signal requires calibration and additional computation and is inefficient.
Accordingly, it is desirable to provide enhanced methods and apparatus for determining acceleration.